This is a very old testing app I did when working with aviation instruments.
It really doesn't do better than any iphone app. Anyways, it might be useful if you are trying to enter in this field.
DO NEVER USE THIS KIND OF SOFTWARE IN IFR CONDITIONS.
DO NEVER USE AVATION SOFTWARE THAT IS NOT DO-178/254.
Keep in mind that DO-XXX is mandatory BEFORE building aircraft software. DON'T EVEN TRY building one by yourself, it will never be on a plane.
It uses serial NMEA0183 messages to work. You will need: QT Creator, Serial GPS (high precision, very low latency)